Original part identification system M- 10- 2003
New part number system adopted in early 1950s and non current models had parts renumbered to conform to the new standard.
39- 20058 standard size
39 – 20992 0.015 oversize
Same rings fit KE7, KF7 and KG7
KG4 has different bore so different pistons and rings
Pars Manual has a lot of informating about what parts
different models share and changes in parts within a production run.
Louis